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Contact: Leslie Stein, 215.898.4982 or stein@monell.org

A Woman’s Nose Knows Body Odor
Women may be sniffing out biologically-relevant information from underarm sweat

PHILADELPHIA (March 07, 2009) – It may be wise to trust the female nose when it comes to body odor.  According to new research from the Monell Center, it is much more difficult to neutralize underarm odor using fragrance when women are doing the smelling.

The findings suggest that underarm sweat contains biological messages or social signals that are especially relevant to females. 

“It is quite difficult to block a woman’s awareness of body odor. In contrast, it seems rather easy to do so in men,” said study lead author Charles J. Wysocki, PhD, a behavioral neuroscientist at Monell.

In the study, women and men rated the strength of underarm odor, both alone and in conjunction with various fragrances.  

The underarm odor alone smelled equally strong to both men and women.  Of the 32 fragrances tested in both men and women, only two successfully blocked underarm odor when women were doing the smelling; in contrast, for men the strength of underarm odor was reduced by 19 fragrances.

The researchers speculate that females are more attuned to biologically relevant information in sweat that may guide women when choosing a mate.

The fragrances were selected to test their ability to block underarm odor through a method known as cross-adaptation.  Olfactory adaptation refers to the loss of sensitivity to an odor when one is constantly exposed to that odor. 
Olfactory cross-adaptation occurs when the nose adapts to one odor and then also becomes less sensitive to a second odor.

Wysocki noted that in earlier studies, men and women did not differ in their ability to cross-adapt to non-biological odors.  “Taken together, our findings indicate that human sweat conveys information that is of particular importance to females.  This significance would explain why it is so difficult to block women’s perception of sweat odors.”

Not only were women better smellers, but male odors were harder to block than female odors.  Only 19 percent of the fragrances reduced the intensity of male underarm odor, while over half successfully blocked female underarm odor.

To collect sweat odors, underarms of male and female donors were injected with epinephrine to stimulate secretions from the underarm apocrine glands. Odorless themselves, apocrine secretions produce the characteristic sweat odors when hydrolyzed—broken down—by bacteria on the skin’s surface.  

Apocrine secretions from donors were collected in small tubes and hydrolyzed with sodium hydroxide to release underarm odor.

Two sensory panels tested each fragrance for its ability to block perception of the underarm odor through cross-adaptation.  One panel evaluated fragrances for their ability to counteract female underarm odor; the second panel judged the effectiveness of fragrances against male odor.  Each panel contained both men and women.

Panelists first rated the intensity of underarm odor. They then continued to rate underarm odor intensity while sniffing a fragrance for 2-1/2 minutes.  A drop in intensity ratings for the underarm odor indicated that the fragrance was a successful cross-adapting agent, capable of neutralizing the odor.

“Men and women differ in how they perceive body odors from both their own and the opposite sex,” summarized Monell scientist George Preti, PhD, an analytical organic chemist who co-led the research with Wysocki.  “This appears to be related to differences in odor quality, not intensity.”

Preti added a practical comment, “Because women appear to be more sensitive and aware of odors, perhaps men should allow their female partners to select their fragranced products.”

The study appears online in Flavour and Fragrance Journal.  Also contributing to the research were Monell researchers Jennifer Louie and Manjindar Gill; James Leyden (University of Pennsylvania); David Blank (Dartmouth College); Les Smith (Coty Inc.); and, Keith McDermott (Symrise Inc.).

The Monell Chemical Senses Center is an independent nonprofit basic research institute based in Philadelphia, Pennsylvania. Monell advances scientific understanding of the mechanisms and functions of taste and smell to benefit human health and well-being.  Using an interdisciplinary approach, scientists collaborate in the programmatic areas of sensation and perception; neuroscience and molecular biology; environmental and occupational health; nutrition and appetite; health and well-being; development, aging and regeneration; and chemical ecology and communication. For more information about Monell, visit www.monell.org.

The Monell Chemical Senses Center is a nonprofit basic research institute based in Philadelphia, Pennsylvania. For 38 years, Monell has been the nation’s leading research center focused on understanding the senses of smell, taste and chemical irritation: how they function and affect lives from before birth through old age. Using a multidisciplinary approach, scientists collaborate in the areas of: sensation and perception, neuroscience and molecular biology, environmental and occupational health, nutrition and appetite, health and well being, and chemical ecology and communication. For more information about Monell, please visit www.monell.org.